Design optimization of cruciform specimens for biaxial fatigue loading
Journal Title: Frattura ed Integrità Strutturale - Year 2014, Vol 8, Issue 30
Abstract
In order to correctly assess the biaxial fatigue material properties one must experimentally test different load conditions and stress levels. With the rise of new in-plane biaxial fatigue testing machines, using smaller and more efficient electrical motors, instead of the conventional hydraulic machines, it is necessary to reduce the specimen size and to ensure that the specimen geometry is appropriated for the load capacity installed. At the present time there are no standard specimen’s geometries and the indications on literature how to design an efficient test specimen are insufficient. The main goal of this paper is to present the methodology on how to obtain an optimal cruciform specimen geometry, with thickness reduction in the gauge area, appropriated for fatigue crack initiation, as a function of the base material sheet thickness used to build the specimen. The geometry is optimized for maximum stress using several parameters, ensuring that in the gauge area the stress is uniform and maximum with two limit phase shift loading conditions. Therefore the fatigue damage will always initiate on the center of the specimen, avoiding failure outside this region. Using the Renard Series of preferred numbers for the base material sheet thickness as a reference, the reaming geometry parameters are optimized using a derivative-free methodology, called direct multi search (DMS) method. The final optimal geometry as a function of the base material sheet thickness is proposed, as a guide line for cruciform specimens design, and as a possible contribution for a future standard on in-plane biaxial fatigue tests.
Authors and Affiliations
R. Baptista, L. Reis, I. Guelho, M. Freitas, J. Madeira
Keywords
Related Articles
- EP ID EP126866
- DOI -
- Views 60
- Downloads 0
Numerical measures of the degree of non-proportionality of multiaxial fatigue loadings
The influence of the non-proportional loadings on the fatigue life depends on the material ductility. Ductile materials react with a shortening of lifetime compared to proportional loading conditions. For a semidu...
Analysis of the fatigue strength under two load levels of a stainless steel based on energy dissipation
In this paper the fatigue behaviour of a stainless steel AISI 304L is analysed. In the first part of the work the results obtained under constant amplitude fatigue are presented and synthesised in terms of both stress am...
Kinetics of fatigue crack growth and crack paths in the old puddled steel after 100-years operating time
The goal of the authors’ investigations was determination of the fatigue crack growth in fragments of steel structures (of the puddled steel) and its cyclic behavior. Tested steel elements coming from the turn of&...
Critical crack path assessments in failure investigations
This paper presents a case study in which identification of the controlling crack path was critical to identifying the root cause of the failure. The case involves the rupture of a 30-inch (0.76 m) natural gas pip...
Properties and applications of Magnetorheological fluids
This brief introduction describes the mechanical, rheological and magnetic properties of the magnetorheological (MR) fluids for feasible engineering applications. The typical modes of exploiting this te...